Electrical indicator



June l 1926. 1,587,050

H. l.. TANNER ELECTRI CAL INDICATOR Filed April 15, 1922 2 Sheets-Sheet l f 5 Jg Il:

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(MIU I A vwamto'c June 1 1926. 1,587,050

H. L. TANNER ELECTRICAL INDICATOR Filed April 13, 1922 2 Sheets-Sheet 2 HARRY-- ZEN/VER fom/JW lll Patent@ inne i, i326..

entren stares nennen HARRY L. TMNER, @F BRGW, NEW YUF.

nnnc'rnrear. marcaron..

application nieu April 3.6, 19%. Serial No. 652,077.

This invention relates to electrical measuring or indicating instruments and has especial adaptability to the measuring of resistance. T ie principal object of this invention is to devise an instrument of this character which possesses greater accuracy than the existin types, is substantially independent of variation in voltage in the line, and at the saine time is simple and inexpensive in construction.

Referring to the drawings, in which what Il now consider to be the preferred forms of niy invention are shown Fig. 1 is a plan view, with the cover partly broken away, of my improved ohmmeter.

Fig. 2 is a vertical section of the saine on line 2-2 of Fig. 1.

Fig. 3 is a diagrammatic plan View of a modified form of ohmmeter.

Fig. e is a section of the same on line 3 4 of Fig. 3.

Fig. 5 is a wiring diagram oi? the meter.

Fig. 6 is a view corresponding to Fig. l. of another modification.

Figs. 7 and 3 illustrate two :'Eurther slight modications in the shape oit the centralizing member of Fig. 1.

Fig. 9 shows a still dierent forni of centralizing member having a di'erent forni et winding.

Fig. 10 is a transverse section of the same, the coils being omitted. y

Fig. 11 is a `wiring diagram of this form of the invention.

The meter shown in Fig. 1 comprises essentially a hollow coil 1 suitably supported in. a casing 2. Within said casing and preferably at the axis of said coil is a shaft 5 of magnetizable material, such as sott iron. On said shaft is mounted a laterally extending armature 6 of like material and an indicator 7, or pointer. Said armature and pointer are rotatably mounted about the anis of the coil, as by securing both to shaft 5 and pivotally mounting the latter between pivots 3, 4 in said casing. With the construction so far described, it will be evident that the assing of a current through said coil will have no effect on said armature, since as much magnetic ux will pass around through shaft 5, armature 6, and back around through the air, with the armature in one position as another.

To localize the flux and thus centraline the armature l rovide a metallic bar 8, preferably et so iron, positioned to one side of the anis oit the coil and with its axis at an angle to the coil axis. With a straight bar sucli as shown in Fig.- 1, armature 6 if symmetrical, would normally take up the position of Fig. 1. Saidbar is shown as supported on brackets 10, 11 on said casing, being held in place by the top 10 when in place.- About sai bar is placed a coil of wire preferably in the forni of a plurality of opposed windings 12, 13, 1. e., windings which are connected so that current normally passes through them in opposite directions. It will be readily apparent, therefore, that if the am ere turns in the two coils 12, 13 are equa, that no magnetic field will be produced thereby, and that, therefore, armature 6 will remain in the position of Fig. 1. lit, however, one coil is stronger than the other, the armature 6 will be displaced to a new resultant position under the in'uence of the fields produced by coil 1 and by the opposed windings, the amount of the displacement being a function of the dierence in the strength of the current in the opposed windings. Y Y

Referring now vto the wiring diagram of Fig. 5, X represents the` unknown resistance which it is desired. to measure. This it will be seen is connected in series with one of the opposed windings 12, both the resistance X and winding 12 being placed in parallel with'coil 13` and (if desired), a known resistance 15, which may be mounted in the vbase of the instrument, (Fig. 2). -Coil '1 on the other hand, is placed in series with the line. construction, the instrument is made wholly tree from the ei'ects of variation in line voltage, as any change in voltage will change equally the eentralizing torque on armature 6 duel to coil 1. and the decentralizing torque due to the diil'erence iii the action of coils y12 and 13.

The character o the scale 16 on which pointer 7 is readable may be varied b the design of the bar 8 and armature 6, an also by the relative resistance of the coil 13 with its resistance 15 to that of coil 12. For example, if armature 6 is symmetrical and coil 13 has a resistance of 50 ohms, and resistance 15, 150 ohms, and coil 12, 100

By this e5 ohms, the central point on the scale 6 would be 100 ohms, assuming an equal number of A ampere turns in coils 12 and 13.

It an open scale 16 (Fig. 6) at one end were desired, armature 6 may be made 1insymmetrical so as to increase its movements in one direction. As shown in Fig. 6, the scale is open for higher readings thereof. A proper scale may alsobe arrived at by shaping the bar 8 vin various ways. Thus, il a weak centralizing edect is desired, bar 8' may be curved toward the pin 5, (Fig. 6), but not about said pin as a center, as under this condition no centralizing would be secured. 0n .the other hand, a greater centralizing edect may be secured y the opposite curving of said bar as shown at 8" in Fig.. 8, or a similar edect may be secured by bending the ends, 71, 72 of the bar up= ivardly as roughl indicated in Fig. 7.

v A somewhat'di erent method of applying the principles hereinbefore outlined is'sl'iown in Figs. 3 and 4. The three coils l', 12 and 13' are retained and connected as shown 1n Fig. 5, but in place of armature 6, l employ a sott iron rod 60 secured to member 6l on shaft 5. Said rod 'may extend downwardly through coil l.' Also within said coil I di; a pair of s aced sott iron rods 62, 63. Coils 12 and 13 (which in this instance, is shown as a single windingl with an intermediate tap), I place upon t e U magnet 80.

'lhe action of this device is very similar to that already described. lVhen the coils 12 and 13 are of equal strength, the bar 60 will be equally re elled by the like poles of rods 62 and 63 an tralized. As soon as one coil 12 or 13 bea comes the stronger, however, the U magnet will weaken one bar 62 or 63 and strengthen the other, thereby causingl proportional displacement of bar 60 and t e attached pointer 7.

In Figs. 9, 10, and 11 are shown several variations in the manner of constructing the instrument. The centralizing bar 8O in this form has no windings at its center where the armature 6 is, the o posed windings l2 and 13 being slipped on e two ends. In this case also, I prefer to employ auxiliary windings 30, 3l on the ends, which are conf nected .in series with coil l (Fig. il.) and each of which opposes the coil (12 or 13) with which it is interwound. B this means the strength of the decentralizing edect is increased. Also the armature 6 may be divided (Fig. 10) so as to extend to both sides of the bar 80, so as to cut a greater number of the lines of force.

In accordance with the provisions of the patent statutes, I have herein described the principle ,of operation of-m invention, together with the apparatus, w ich I now consider to represent the best embodiment thereof, but I desire to have it understood hence will remain ceinthat the apparatus shown is only illustrative and that the invention can he carried out b other means. Also while it is designe to use the various eatures and elements in the combination and relations described, some of these may be altered and others omitted without interfering with the more general results outlined, and the invention extends to such use.

Having. herein described my invention, what I claim and desire to secure by lietters Patent is l. An ohmmeter comprising the combination with a known resistance, ot a stationary coil, an armature rotatable about the axis thereof, a pair of coils adapted to carry curs rent in opposite directions, a magnetic core for said pair of coils, said pair ot' coils having their anis at an angle to the axis of the drst named coil, means for connecting the said coils and resistance with the unknown resistance so that the current passing through Vsaid iirst named coil divides into parallel circuits one ot which includes the known resistance and one ot said pair of coils and the other the unknown resistance and the other of said coils.

2. An electrical indicating instrument comprising a coil, an armature revoluble about the axis thereof, an indicator coiinected thereto, a bar ot high permeability non-concentrically located with respect to the airis ot said coil and adapted. to centralibze said armature and a winding on said 3. An electrical measuring instrument comprising a coil, an armature revoluble about the axis thereof, an indicator connected thereto, and a sott iron member to one side of the axis of said coil for centralizing said armature and a windingon said member. Y

4. An electrical measuring instrument comprising a coil, an armature revoliible about the axis thereof, an indicator connected thereto, a sott iron-member tor centralizing said armature, a pair ot opposed windings on said member, and means Whereby current is passed throughsaid windings in parallel and then through said rst named coil.

5. An electrical measuring instrument comprising a coil member, an armature member, one ot said members being revoluble about the axis ot' the coil, an indicator connected thereto, a sott iron member tor centralizing said armature, a plurality of opposed windings for shifting the resultant field of force set up by said coil and windings to cause rotation of said indicator and means for inserting the resistance to be measured in circuit with one of said opposed windings.

6. An electrical measuring instrument comprising a coil, an indicator rotatable about the axis of said coil,a magnetic member mounted to rotate with said indicator about the axis thereof, means cooperating. With said coil for centralizing said' member in one position, and means for modifying lthe forces exerted by said rst named means netic linx created by said coil to centralize said armature, and a plurality of windingsfor setting up a field tending to shift the position of maximum flux to rotate said armature through an angle proportionate to the relative strength of the centralizing and decentralizing forces. A

8. An electrical indicating instrument comprising a magnetizable rotatable member, an indicator actuated thereby, a coil for magnetizing said member, magnetic centralizing means adjacent said coil for said member and means for deflecting said member from its normal position.

9. An electrical indicating instrument comprising a magnetizable member, a coil member for magnetizing said member one of said members being rotatable, magnetic centralizing means to one side of said coil for said member and a second coil for deflecting said member from its normal position.

10. An electrical indicating instrument comprising a magnetizable rotatable member, a coil for .magnetizing said member, magnetic centralizing means for said member adapted to localize the magnetic flux produced by said coil and a coil for deflecting the said member in either direction from itsA normal position.

11.' In an ohmmeter, in combination, a coil membenan .armature member, one of said members being rotatable about the axis of the coil, a soft iron member or the like, and a pair of opposed windings on said iron member, the soft iron member being mounted' to one sideA of the axis of the coil. p

In testimony whereof I have affixed my signature.

HARRY L. TANNER. 

